In the field of nuclear physics, the experiments of neutrino have drawn world wide attention in science frontline. In 1956, Clyde Cowan and Frederick Reines directly detected the neutrino in experiment and they were awarded the 1995 Nobel Prize in physics; in 1962, Leon M. Lederman, Melvin Schwartz and Jack Steinberger discovered a second type of neutrino, i.e. muon neutrino and they thus wined the 1988 Nobel Prize in physics; Raymond Davis Jr. and Masatoshi Koshiba were jointly awarded the 2002 Nobel Prize in Physics, in which Davis for his pioneer work on cosmic neutrinos in 1968 and Koshiba for the first real time observation of supernova neutrinos in 1987. However, till now the questions about neutrino mass scale and the transformation between different types of neutrinos are still basic scientific issues need to be answered in nuclear physics (Zhixun Huang, Engineering Science, 2002, 4(10), 7-10).
In the research field of neutrino, the decay rate (half life) of double beta decay is an important issue because the relationship between decay rate (half life) and absolute mass of neutrino can be expressed as following:τ1/2−1=Gthr(Q,Z)|MGr|2|(mv)|2 
So, the absolute mass of neutrino can be known through the half life detection of double beta decay. Till now, double beta decay experiments seem to be still the only way to detect the absolute mass of neutrino (R. Ardito et al., Annual Report for CUORICINO and CUORE 2004, 17-37).
Tellurium dioxide (TeO2) single crystal is an excellent acousto-optic (AO) material, which can be used in various kinds of AO devices, such as AO deflectors, AO modulators, AO resonators and tunable filters (S. Kumaragurubaran et al., J. Crystal Growth 2000, 211, 276-280; P. Veber et al., J. Crystal Growth 2004, 270, 77-84).
Besides, TeO2 single crystal has double beta decay property, which can be used in nuclear physics as double beta decay source (I. Dafenei et al., Nucl. Instrum. Meth. A 2005, 554, 195-200). As the natural abundance of 130Te is high (34%, the highest level of all natural double beta decay source), TeO2 single crystal can be used as double beta decay source without enrichment process, thus the cost is much lower.
However, if TeO2 single crystal is used as double beta decay source for the detection of neutrino mass, the crystal itself should be of high purity, especially with a content of some radioactive impurities such as U and Th deceased to a level of 10−13 g/g.
Chinese patent ZL03141999.2 reported the Bridgman growth of TeO2 single crystal with large size and good quality, through which the radioactive impurities such as U and Th decreased to a level of 10−12 g/g, but still couldn't reach the level required for double beta decay source.
Until now (filing date of the present invention), we haven't found any reports about decreasing impurities to prepare high pure TeO2 single crystal.